Preheat temp setting duration when using AOYUE (etc.) 853A rework pre-heater

[wb0gaz]

Need to handle a small reflow task (this isn't a repair task, but this kind of requirement probably comes up during repair so thought i'd start here.)

I'm going to use an Aoyue (etc.) 853A rework pre-heating unit before hot air soldering.

Any guidance available on what temperature preset and pre-heat duration I should use?

Any guidance available on what workpiece temperature I should measure before using hot air to reflow?

Would a Flir-type IR imager be sufficient to measure temp of the workpiece?

Solder will be either 63/37 PbSn or 57Bi42Sn1Ag paste. The workpiece is small FR4 PCB.

Thanks  for any advice (or pointers to information on this topic.)

[BreakingOhmsLaw]

Don't bother measuring the temperature, you don't need rocket science precision here.
I preheat to 125°C on lead free PCB and then spot-heat the areas of interest with hot air set to 360.
If you used Bismuth tin, you'll need to drop the temperature to 90 plate /145 air.

Don't throw the PCB on the already heated hot plate, start with a cold(ish) plate to reduce thermal stress.

[wb0gaz]

Hello BreakingOhmsLaw, that is very much helpful!

1. I will begin from cold start on device, with workpiece already placed.

2. Shall I set pre-heat machine temperature (it's set-point for radiated heat) to 125C? For this pre-heat machine, there is ~2cm distance from thermal element (below) to workpiece (above), suspended by metal structure to keep PCB away from thermal element.

3. How long should I wait (once pre-heat machine reaches set point, until workpiece reaches OK temperature?

Thank you again!

[Silicium81]

Hello,
I have a YIHUA 853A preheat unit. To get the PCB to 100°C, I need to set the heater temperature to 250°C. The safest thing is to measure the temperature of the PCB with a thermocouple!

[wb0gaz]

That (preheat setting) was what I was completely uncertain about.

What do you use for a thermocouple, and how do you apply it for this purpose?

Thanks!

[Silicium81]

The thermocouple bracket:





In fact, I made a small system to be able to remove the BGA (and put them back after reballing). The thermocouple is used to regulate the upper circuit temperature by generating a controlled reflow profile. But before starting the upper heating, it indicates the temperature due to the lower heating.

https://vae-tech.forumactif.org/t239-reparation-bga-ou-rebillage (in french  )

(sorry for my english 'google translate'  )

[wb0gaz]

Thank you excellent detail!

Hope for BGA in future!!!

Now I will find DMM + Thermocouple solution.

Thank you again,

Dave

[Silicium81]

Thank's, For low price thermometer with thermocouple, search TM-902C on aliexpress 

[wb0gaz]

Thanks so much, Silicium81!

I had searched unsuccessfully for that sort of device, evidently wrong search terms.

Order now placed.

Very much appreciate your helpful detail - this is how to solve the requirement!

Dave

[testpoint1]

Thank you excellent detail!

Hope for BGA in future!!!

Now I will find DMM + Thermocouple solution.

Thank you again,

Dave

Fluke 87V and 80BK-A probe

[wb0gaz]

Rats - I knew i had a thermocouple probe somewhere, came with a DMM, long since lost...

Oh well, that's a helpful pointer!

Dave